The present invention relates to a delivery valve of an internal combustion engine, e.g. diesel engine, high-pressure fuel pump
The high-pressure fuel pumps of modern diesel engines operate at high pressures of up to 1,600 bars, and the delivery valves must ensure constant delivery pressure with no fall in pressure or pressure peaks over and above the desired pressure.
Various types of delivery valves are known, each of which comprises a shutter pushed elastically to close a delivery conduit. In one known valve, the shutter is defined by a ball, which is pushed against its seat by a cylindrical helical spring having a first end resting on a fastening member on the pump. The other end of the spring acts on the ball by means of a cap, which slides axially inside a cylindrical hole on the pump and, together with the ball, defines the movable part of the valve.
The cap of the above known valve has a wall engaging the ball; a shoulder on which said first end of the spring rests; a cylindrical surface enclosing the turns of the spring; and axial cap guiding members in the hole and/or on the fastening member. The cap is therefore complicated and expensive to produce and makes the movable part of the valve relatively heavy, thus resulting in a certain amount of inertia in turn resulting in severe oscillations in the delivery pressure of the pump.
It is an object of the invention to provide a delivery valve of the above type, which is highly straightforward and cheap to produce, and has a lightweight movable part to eliminate the aforementioned drawbacks typically associated with known valves.
According to the present invention, there is provided a delivery valve of an internal combustion engine high-pressure fuel pump, comprising a shutter normally pushed by a helical compression spring to close a delivery conduit of the pump communicating with a compression chamber; said spring having a first end resting against a surface of a fastening member fitted in fluidtight manner to the pump; characterized in that a second end of said spring acts directly on said shutter; valid fastening member having a pin coaxial with said conduit and for guiding said spring; and said pin being of such a length as to limit the travel of said shutter to a predetermined value.